Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $201.48   7.523%   $216.6373   $216.64   $216.65   $216.60  
  Purchase #2 $58.49   4.321%   $61.0174   $61.02   $61.00   $61.00  
  Purchase #3 $90.40   4.185%   $94.1832   $94.18   $94.20   $94.20  
  Purchase #4 $143.37   8.530%   $155.5995   $155.60   $155.60   $155.60  
  Purchase #5 $52.48   12.350%   $58.9613   $58.96   $58.95   $59.00  
  Purchase #6 $107.78   5.668%   $113.889   $113.89   $113.90   $113.90  
  Purchase #7 $192.59   7.603%   $207.2326   $207.23   $207.25   $207.20  
  7 purchase totals = $846.59       $907.5203   $907.52   $907.55   $907.50